Subscriber dataset properties

The following table shows the subscriber dataset properties.
Field
Description
Name
Enters the subscriber dataset name. The name is used for FactoryTalk Linx Gateway identification, and it will not be sent to the broker.
Description
Enters the subscriber dataset description.
Topic
Enters the topic name. The topic must match the publisher’s topic. Datasets cannot subscribe from a broker with the same topic, otherwise, the subscriber function will not work.
Payload Format
Selects the payload format aligning with the publisher.
  • FactoryTalk Optix Format
    FactoryTalk Optix can use the FactoryTalk Linx Gateway MQTT data.
  • Rich Format
    FactoryTalk Linx Gateway MQTT provides the rich MQTT structure that is the same as the data from FactoryTalk Edge Gateway MQTT.
  • Flat Format
    FactoryTalk Linx Gateway MQTT provides the flatten MQTT structure for Plex APM applications that is the same as the flat data from FactoryTalk Edge Gateway MQTT.
For more information, see Payload format examples.
Quality of Service (QoS)
Defines the effort produced by the broker or client to ensure that a message is received. The broker sends messages at any QoS level.
  • At most once (QoS 0)
    The message is delivered once, with no confirmation.
  • At least once (QoS 1)
    The message is delivered at least once, with confirmation required.
  • Exactly once (QoS 2)
    The message is delivered once by using a four-step handshake.
Maximum Number of Tags to Write Simultaneously
Specifies the maximum tag number that the client can write to the controller in a writing cycle.
Minimum Writing Interval (Millisecond)
Specifies the minimum interval between each writing cycle. If a new value arrives after the same item was previously written but before the minimum writing interval has expired, the new value will be held until the minimum writing interval expires.
Write Strategy When Previous Value Is Pending
Selects the write strategy when a new tag value is received but a previous tag value is waiting to be written.
  • Discard new value
    When the same tag is pending for writing, the previous values will be retained.
  • Discard previous value
    When the same tag is pending for writing, the previous values will be dropped.
Only write changed values
Turns on writing changed values to the same tags only.
FactoryTalk Linx Gateway
 will compare each incoming value to the previous incoming value for the same item and only perform a write if the new value is different, which can save the system resources.
Log error messages when writing tags failed
Turns on error message logging when tag writing failed.
Log diagnostic messages when writing tags succeeded
Turns on diagnostic messages logging when tags writing succeeded.
  • Log as audit message
    When it is selected, all messages will be logged as the audit message.
  • Log as diagnostic message
    When it is selected, all messages will be logged as diagnostic messages.
Frequent tag writes will cause a high number of diagnostic messages.
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